Textile fabric to resist penetration is often formed from strands, or filaments, of high strength yarn that are tightly woven and arranged in a layer and then combined with other layers to form a penetration resistant panel. In some cases, each layer may be combined with a resin to bind the yarns together and distribute the penetration force between yarns in each layer. The resin would be a small percent by weight of the layer and the flexibility of the layer would be retained, so the panel would remain flexible. In other cases, the layer is combined with resin and then multiple layers are laminated together under pressure and elevated temperature so the layers are bonded to each other to form a monolithic structure that is a rigid panel often, the rigid layers and panels would use more resin than the flexible layers and panels. Either the flexible or rigid panel can be used in a garment by inserting the panels in pockets in the garment, where the pockets are located in strategic areas of the body of the wearer to protect vital organs. Uses for such a garment would be for example, meat cutter aprons, chainsaw chaps, "bulletproof" vests or overcoats, protective gloves, boots, tents, or the like.
In a process using weaving to hold the strands together, the strands are guided over and under adjacent strands which is a slow process and one that does not permit much variety in forming the fabric unless complex weaving patterns and complex machines are used. In a regular loom for weaving fabrics, individual yarn strands are used and the weft yarns are added one at a time. The yarns are shifted over one another and are forced tightly into position which often causes structural damage to the individual yarns. Coated yarns exhibiting high friction against other yarns cannot be readily woven. For a given weaving process (machine) and yarn denier there is a limit to the number of yarns that can be placed in a given area for a single layer since the yarns cannot readily be overlapped. Binder resin is commonly introduced by the addition of sheets of material to the outer surfaces of the woven fabric. There is a need for a process that permits more variety in placing yarn and resin in fabrics, and a need for a process that rapidly places many yarns at a time without high stress and abrasion to the yarns.
In ballistic layer structures made from yarn, the yarns in the layer generally should completely cover an area without any openings. The yarns should be tightly packed or overlapped so no openings exist in the structure that would make penetration by a projectile or hand held weapon easy. Stacking of the layers would add strength, but basic area coverage would come from each layer.
There is a need for a way to rapidly form a flexible or rigid composite fabric from strands of yarn comprising structural yarn and binder yarn, or comprising strands of structural yarn and binder sheets, or comprising structural yarns coated with binder resin. There is a need for an article that has controlled reliable overlap between individual yarns in a layer to optimize structural yarn use and produce an article that accommodates tolerance variations in yarn and laydown accuracy to provide high quality product yield.
A series of patents to Oswald (U.S. Pat. No. 4,600,456; U.S. Pat. No. 4,830,781; and U.S. Pat. No. 4,838,966) lay down a pattern of partially vulcanized rubber coated strips, or cords, to make a loop of pre-formed reinforcing belt for a vehicle tire. The strips or cords are stuck together wherever they touch to make a relatively stiff structure. The cords are laid in a "zig-zag repeating pattern with succeeding lengths of the strips being displaced from each other. The cord lengths are interleaved with lengths of cords disposed at an opposite angle . . . . This interleaving relationship results in a woven structure". The stickiness of the partially vulcanized rubber apparently holds the cords in place to a forming surface and to each other until the belt is assembled with other elements of the tire and molded under heat and pressure to form a completed tire.
The process practiced by Oswald and others uses one or a few cords that are traversed back and forth across the belt numerous times to complete one circumference. This is believed to result in a stratified structure where the cords in any one stratum are sparsely arrayed, but they do not completely cover the belt area. It is only after repeated zig-zag passes over the belt area that the area becomes sparsely covered with cord. Due to the repeated zig-zag passes of only a few cords, it is believed that within any one stratum there are cords laid down in two different directions that do not cross one another. Cords that cross one another would be in different stratum. These structural features of the reinforcing belts are symptomatic of a process that lays down only a few cords at a time and must make many repeated passes over the belt area to get coverage of the area.
A process taught by Prevorsek et al in U.S. Pat. No. 5,677,029 teaches a penetration resistant composite layer made by bonding a polymeric layer to a fibrous layer. Several of these composite layers are then combined in a laminated structure to form a ballistic structure that resists penetration by bullets. In example 2 where ballistic performance is illustrated, the fabric layer is a woven fabric so the limitations of weaving are still present. The advantage of adding the bonded polymeric layer, is that fewer fabric layers are required and a lower weight structure results to achieve the same ballistic performance as fabric layers without the bonded polymeric layers.
There is a need for a simple non-weaving process that can make penetration resistant fabric structures by laying down many high strength yarns simultaneously over a fabric area to sparsely cover it rapidly and with high accuracy. There is a need for a fabric structure that provides some flexibility in designing how and where to place binding resins in the structure to accommodate different yarns, resins, and manufacturing processes. There is a need for a fabric structure which can accommodate a range of yarns to cover an area so different strength fabric layers can be made with a single machine and yarn just by varying simple machine adjustments. There is a need for a penetration resistant article that has individual yarn overlap in each layer to optimize yarn usage and accommodate tolerance variations in yarn dimensions and laydown accuracy.